Introduction.

Asian rust caused by the Phakopsorapachyrhizi fungus is the most destructive disease affecting soybeans. The development of transgenic plants that carry defensins offers an alternative to protect the crop. Defensins are small antimicrobial peptides present in plants that play a role in their natural defense mechanism.

Methods.

Soybean embryogenic axes were transformed with the NmDef02 defensin gene isolated from Nicotianamegalosiphon, using an optimized ballistics transformation methodology that selects shoots resistant to the herbicide glyphosate. The transgenic clones were analyzed molecularly. Nodulation was evaluated in transgenic plants inoculated with the nitrogen-fixing bacterium Bradyrhizobiumjaponicum. The transgenic clones were evaluated in the field against natural infection with P. pachyrhizi, licensed by the National Center for Biological Safety.

Results and Discussion.

Glyphosate resistant transgenic clones with high transformation efficiency were obtained. Integration and expression of the transgene was confirmed by PCR, Southern blot and qRT-PCR. Efficient nodulation was achieved in roots of transgenic plants inoculated with B. japonicum bacterium. The severity of rust, fungal biomass and defoliation in plants were significantly lower in the transgenic clones. The constitutive expression of the NmDef02 gene in the transgenic clones induced a high resistance to P. pachyrhizi in the field, being higher in plants of the clone Def1. It is concluded that it is the first time that soybean plants have been transformed with a defensin, using a transformation methodology adapted to Cuban genotypes. The expression of the transcript in soybean plants does not affect nodulation by B. japonicum, which is essential for atmospheric nitrogen fixation. It is the first report of resistance to Asian rust in transgenic soybean plants that express the defensin NmDef02.

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